Processes for the recovery and purification of uranium



Nov. 20, 1956 R. Q. BOYER 2,771,339

PROCESSES FOR THE RECOVERY AND PURIFICATION OF URANIUM Filed Sept. 2, 1944 3 Sheets-Sheet 1 CONDENSATE SCRUBBING AND HING AND AMA 5] PARTS OF QALUTRON u WATER W'TH HOT WATER CONDENSING s EVI NG SOL/D lMPUR/T/ES {WASH WATL-R MAKE UP WATER OXIDIZING TO DISCARD 2 OR SALVAGE SOLUTION U024!- Cu ./-'e*** FILTERING N/** V PREC/P/TATE C Co F/LTRATE -Iz-f EVAPORATING Fem To DISCARD m 0R SALVAGE PRECIPITATING OH AND FILTERING WAT/TE PREC/P/ TA TE cu (NH3)4 4)2 2 7 1w /NH3)4 Fe(0H) C/-(0H)3 d TO DISCARD TO FURTHER OR SALVAGE TREATMENT a INVENTOR. g' BY Robe/'7 Q. Boyer ATTORNEY.

Nov. 20, 1956 R. Q. BOYER 2,771,339

PROCESSES FOR THE RECOVERY AND PURIFICATION OF URANIUM Filed Sept. 2, 1944 3 Sheets-Sheet 2 CONDENSA TE SOLUTION AND MAKE UP 00 CONDENSI NG VA POI? EVAPORATI NG (U 3 OR(Z)HC/ & H202 0/?(3) H2504 .2 H2 0 CONCENTRA TED SOLUTION U021?L Fe F/LTRA 7'5 r-MH- N/(NHJ)4** N;

PRECIPITATING {NI/40H AND FILTERING PREC/P/TATES 125 3 To DISCARD CH0): OR SALVAGE F To .FURTHER 2 TREATMENT INVENTOR.

Roberf Q. Boyer 1 ATTORNEY.

Filed Sept. 2, 1944 Nov. 20, 1956 R. Q. BOYER 2,771,339

PROCESSES FOR THE RECOVERY AND PURIFICATION OF URANIUM 3 Sheets-Sheet 3 STARTING MATERIAL FROM PR'OR PREC/P/TA TES TREATMENT (/VH4)2U207 LARGE AMI Fe (Of/) LARGE AMT. Cr(0/-/)3 SMALL AMT.

L DISSOLVING SOLUTION U021"; Fe 'I'f'l' Cr *f'l ADJUSTING NI-l 0H PH SOLUTION UOz' Fe 41''! C,-

REDUCING o U++++ 'Z (NH4)2 5204 FG Fe COM PLEXI NG OF SOLUTION U *1"!- Fe ff ADJUSTING OF pH AND FILTERING TO DISCARD PREC/P/TA TE U(0/-l) on SALVAGE CALCI NI NG Wmpop 9 125m"; B Robe/'7 Q. Boyer United States Patent I, O a

PROCESSES FOR THE RECOVERY AND PURIFICA- TION OF URANIUM Robert Q. Boyer, Berkeley, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application September 2, 1944, Serial No. 552,548

Claims. (Cl. 23-145) The present invention relates to processes of producing uranium enriched with U and more particularly to improvements in certain steps of the process disclosed in the copending application of James M. Carter and Martin D. Kamen, Serial No. 532,159, filed April 21, 1944 which issued as Patent No. 2,7 58,006 on August 7, 1956.

It is an object of the invention to provide an improved process of reclaiming uranium from a calutron.

Another object of the invention is to provide an improved process of recovering the residue of a uranium compound which has been subjected to treatment in a calutron from the parts of the calutron disposed in the source region thereof upon which the residue is deposited.

Another object of the invention is to provide an improved process of recovering metallic uranium enriched with U from the collector of a calutron upon which the enriched metallic uranium is deposited.

A further object of the invention is to provide an, improved process of purifying uranium which has been recovered from a calutron.

A further object of the invention is to provide a process of reclaiming uranium from a wash solution derived from a calutron in which the wash solution is first reduced and then the uranium is precipitated in its lower valence state away from the metal impurities in the wash solution.

A still further object of the invention is to provide a process of reclaiming uranium from a wash solution, derived from a calutron in which the uranium is precipitated away from metal impurities in the wash solution as uranous hydroxide.

The invention both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the fol lowing specification taken in connection with the accompanying drawings, in which Fig. 1 illustrates a portion of the flow diagram of the present process, indicating the recovery of the residue of UCL; from the parts of the calutron disposed in the source region thereof upon which it is deposited, and the initial steps of the subsequent purification of the uranium; Fig. 2 illustrates another portion of the flow diagram of the present process, indicating the recovery of the metallic uranium from the collector of the calutron upon which it is deposited, and the initial steps of the subsequent purification of the uranium; Fig. 3 illustrates a further portion of the flow diagram of the present process, indicating the subsequent steps of the purification of the recovered uranium.

At the outset, it is noted that a calutron is a machine of the character of that disclosed in the copending application of Ernest 0. Lawrence, Serial No. 557,784, filed October 9, 1944 which issued as U. S. Patent 2,709,222 on May 22, 1955, and is employed to separate the constituent isotopes of an element and more particularly to increase the proportion of a selected isotope in an element containing a plurality of isotopes in order to produce the element enriched with the selected isotope. For

2,771,339 Patented Nov. 20, 1956 2. example, the machine is especially useful in producing uranium enriched with U Such a calutron essentially comprises means for vaporizing a quantity of material containing an element which is to be enriched with a selected one of its several isotopes; means for subjecting the vapor to ionization, whereby at least a portion of the vapor is ionized causing ions of the several isotopes of the element to be produced; electrical means for segregating the ions from the un-ionized vapor and for accelerating the segregated ions to relatively high velocities; electromagnetic means for deflecting the ions along curved paths, the radii of curvature of the paths of ions being proportional to the square roots of the masses of the ions, whereby the ions are concentrated in accordance with their masses; and means for de-ionizing and collecting the ions of the selected isotope thus concentrated, thereby to produce a deposit of the element enriched. with the selected isotope.

More particularly in operating a calutron for the separation of uranium isotopes a volatile compound of uranium, e. g., UCL; is employed as the compound which is vaporized and ionized. These operations are conducted in the ion source of the calutron and, since only a fraction of the material is actually ionized and accelerated therefrom, a residual deposit of UC14 is produced on' stainless steel surfaces in the source region. The accelerated ions of the uranium isotopes are separated by passage through the magnetic field of the calutron and, therefore, uranium enriched in isotopes U and U is deposited in the first. pocket of the collector while uranium enriched in the isotope U is deposited in the second pocket. Some uranium and chloride ions of different charge to mass ratios miss the collector and are deposited on various interior surfaces of the calutron.

Ordinarily, in plant operations, it is necessary to recycle the separated material to enhance the content of the desired isotope. However, since a large volume reduction has occurred, the plant requires only a small number of second-stage calutrons as compared to the number of first-stage machines; however, the separated materials become more valuable and it is highly desirable that the chemical separation processes are efficient and economical.

More particularly, in the cascaded plant arrangement, metallic uranium singly enriched with U and deposited in the first pocket of the collector of the first-stage calutron is removed therefrom by an acid wash process, purified, converted to UCL; and reprocessed in a second-stage calutron. The residual deposit of UCl4 is removed from the source region of the first-stage calutron by a water wash process, the solution combined with an acid wash solutionobtained from the second pocket of a secondstage calutron, the composite solution is purified and the uranium is reprocessed in the first-stage calutron. The uraniumdoubly enriched in U from the first pocket of the collector of the second-stage calutron, is recovered by an acid wash process, purified and converted to a standard compound for commercial use. The singlyenriched residual UCI4 fromthe source region of the second-stage calutron is recovered by a water Wash process, the solution combined with acid Wash solution derived from the first pocket of the first-stage calutron collector, the composite solution is purified and the singlyenric'hed material is reprocessed in the second-stage calutron. Uranium which is unduly impoverished with reference to U is recovered from various portions of the various calutrons and eliminated from the U isotope enrichment cycle.

Considering now the details of the recovery of the UCl4 residue from the parts of either a first-stage or a second-stage calutron disposed in the source region thereof, reference is made to the portion of the flow diagram;

in the source region thereof, principally the source-' region end of the liner, are scrubbed and washed with hot water, whereby the residue of UCli deposited thereon is dissolved; and various impurities including copper, iron, chromium, nickel and carbon, are introduced in the water wash, due to the fact. that the various parts of the calutron which are thus washed with hot water are formed of the materials mentioned. The wash water is then sieved in order to remove any solid impurities which may be picked up, such, for example, as small pieces of metal and carbon. These solid impurities may be either discarded or subjected to salvage treatment in order to recover any occluded uranium. The sieved wash water is then treated with an oxidizing agent such as H202 by adding a slight excess of ten percent H202 and agitating the solution in order to oxidize the various contained materials. For example, the wash water prior to the step of oxidation may contain suspended U(H)4 and bits of copper and carbon, dissolved uranium in the +4 and +6 valence states, as well as dissolved copper, iron, nickel, chromium and possibly other metals in one or more of the positive valence states. Hence, as a result of oxidation all of the uranium is put in solution as uranyl ion, suspended copper is put in solution as cupric ion, and other dissolved materials are put in their higher stable valence states, if they are not already in such state. Carbon is not oxidized by this treatment. The effect of the oxidation on the various materials contained in the wash solution may be indicated as follows:

Accordingly, the oxidized wash water contains at least the following: U02++, Cu++, Fe+++, Cr+++, Ni++ and C (carbon). The oxidized wash water is then filtered in order to remove 0, which may be discarded or subjected to salvage treatment in order to recover any occluded uranium.

In the event this filtrate is rather dilute, it may be concentrated by evaporation; otherwise, this step is omitted. In the event the filtrate is concentrated by evaporation, the water vapor which is driven off is condensed, and to it is added enough makeup water in order to provide a new wash solution which is used again to wash the parts of the calutron disposed in the source region thereof, in the manner previously explained. This step, comprising condensing and re-using the water vapor which is driven otf the filtrate incident to concentration by evaporation, is advantageous in view of the fact that any uranium entrained in the water vapor is not lost to the outside.

The original filtrate mentioned above, or the concentrated filtrate following evaporation, in the event this step is employed, is then subjected to ammonia treatment, either with excess NH: gas or carbonate-free NHiOH, whereby (NH4)2U20'1, Fe(0H)3 and Cr(0H)a are precipitated away from the copper and nickel, which remain in solution in the form of ammonio complex ions, C11(NII3)4++ and Ni(NH3)4++. The solution is then filtered and the precipitate, consisting of ammonium diuranate, ferric hydroxide and chromic hydroxide, is then washed with water containing about one percent NH40H and one percent NH4NO3, in order to eliminate occluded copper and nickel ammonio complex ions. The filtrate, containing the copper and nickel ammonio complex ions, is then discarded or subjected to salvage treatment in order to recover any uranium contained;v and the initially purified precipitate of (NH4)2U207, Fe(0H)a and Cr(0H)a is then stored for further treatment.

It will be understood that the stored precipitate derived from the parts of the first-stage calutron disposed in the source region thereof, as explained above, comprises uranium of natural or normal composition with reference to U while the stored precipitate derived from the parts of the second-stage calutron disposed in the source region thereof, as explained above, comprises uranium which is singly enriched with U Considering now the details of the recovery of the metallic uranium, singly enriched with U from the first pocket of the collector of the first-stage calutron, or of the metallic uranium, doubly enriched with U from the first pocket of the collector of the second-stage calutron, reference is made to the portion of the flow diagram illustrated in Fig. 2. The inner surfaces of the first pocket of the collector of the calutron are etched with one of a number of acid solutions, whereby the deposit of metallic uranium, either singly or doubly enriched with U is dissolved; and various impurities including iron, chromium and nickel are introduced in the acid wash solution, due to the fact that the inner surfaces of the first pocket of the collector of the calutron which are thus etched with the acid solution are formed of stainless steel which comprises the materials mentioned. Accordingly, the wash acid contains at least the following ions: U02++, Fe+++, Cr+ and Ni++.

A suitable acid wash solution which may be employed for the purpose mentioned comprises an aqueous solution containing HNOa (approximately twelve percent). Another suitable acid wash solution comprises an aqueous solution containing HCl (approximately two percent) and H202 (approximately 0.5 percent). A further suitable acid wash solution comprises an aqueous solution containing H2S04 (approximately eighteen percent) and H202 (approximately ten percent). Thus, it will be understood that the first acid wash solution comprises an eliminate occluded nickel ammonio complex ion.

oxidizing acid, whereas the second and third acid wash solutions comprise a separate oxidizing agent such as H202. Hence, the acid wash soultion employed in any case produces an oxidizing etfect upon both the uranium and the metal impurities which are dissolved therein.

In the event the wash acid is rather dilute in the ions mentioned, it may be concentrated by evaporation; other wise, this step is omitted. In the event the wash acid is concentrated by'evaporation, the vapor which is driven off is condensed and to it is added enough makeup HNOa, 0r HCl and H202, or H2804 and H202, depending upon the composition of the original wash acid employed, in order to provide a new wash acid which is again used to wash the first pocket of the collector of the calutron, in the manner previously explained. This step, comprising condensing the vapor which is driven off the wash acid incident to concentration by evaporation, is advantageous, in view of the fact that any uranium entrained in the vapor is not lost to the outside.

The original wash acid mentioned above, or the concentrated wash acid following evaporation, in the event this step is employed, is then subjected to ammonia treatment either with NH; gas or carbonate-free NHiOH, whereby (NH4)2U20-1, Fe(0H)3 and Cr(0H)3 are precipitated away from the nickel which remains in solution in the form of ammonio complex ion, Ni(NHa)4 The solution is then filtered and the precipitate, consisting of ammonium diuranate, ferric hydroxide and chromic hydroxide, is then washed with water containing about one percent NHiOH and one percent NH4N03, in order to The filtrate containing thenickel ammonio oomplex ion is then discarded or subjected to salvage treatment in order to recover any uranium contained; and the initially purified precipitate of (NH4)2U20'1, Fe(0H)3 and Cr(0I-I)a is then stored for further treatment.

1 It will be understoodthat the stored precipitate derived from the first pocket of the collector or the first-stage calutron, as explained above, comprises uranium which is singly enriched With U while the stored precipitate derived from the first pocket of the collector of the second-stage calutron comprises uranium which is doubly enriched with U The metallic uranium, impoverished with respect to U and deposited in the second pocket of the collector of the first-stage calutron, may be recovered merely by etching the inner surfaces of the second pocket of this collector with a suitable wash acid of the character mentioned above, whereby this deposit of metallic uranium is dissolved. This acid Wash is then discarded, as it contains so little U that further processing thereof is not feasible.

On the other hand, the metallic uranium which has been first enriched with respect to U and subsequently impoverished with respect to U and deposited in the second pocket of the collector of the secondstage calutron, may be recovered by etching the inner surfaces of the second pocket of this collector with a suitable wash acid of the character mentioned above, whereby this deposit of metallic uranium is dissolved; and various impurities, including iron, chromium and nickel are introduced in the acid wash solution, due to the fact that the inner surfaces of the second pocket of the collector of the calutron which are thus etched with the acid solution are formed of stainless steel which comprises the materials mentioned. Accordingly, the wash acid contains at least the following ions: UOz++, Fe+++, Cr+++ and Ni++. The considerations concerning whether the wash acid should be concentrated are the same as those previously noted. In any case, either the original wash acid mentioned above, or the concentrated Wash acid following evaporation, in the event this step is employed, is then analyzed in order to determine the U content thereof. In the event the analysis indicates that the U content of this wash acid is at least as great as natural or normal uranium, it is conserved for further treatment; on the other hand, in the event the analysis indicates that the U content of this wash acid is less than that of natural or normal uranium, it is discarded, as further processing thereof is not feasible.

Assuming that the analysis indicates that the U content of this conserved wash acid is at least as great as that of natural or normal uranium, it is subjected to initial purification by the ammonia process previously described, whereby a precipitate of (NH4)2U2O7, Fe(OH)s and Cr(OH)s is obtained, which is then stored for further treatment.

To the stored precipitate derived after initial purification from the parts of the first-stage calutron disposed in the. source region thereof, there is added the stored precipitate derived after initial purification from the second pocket of the collector of the second-stage calutron, in order to produce a first composite precipitate; this first composite precipitate comprises uranium of substantially natural or normal composition with reference to U Also, to the stored precipitate derived after initial purification from the parts of the second-stage calutron disposed in the source region thereof, there is added the stored precipitate derived after initial purification from the first pocket of the collector of the first-stage calutron, in order to produce a second composite precipitate; this second composite precipitate comprises uranium which is singly enriched with U Finally, the stored precipitate derived after initial purification from the first pocket of the collector of the second-stage calutron constitutes a third composite precipitate; this third composite precipitate comprises uranium which is doubly enriched with mass Considering now the details of the subsequent purification of one of the composite precipitates described above, comprising (NH4)2U2O7, Fe(OH)s and Cr(OH)a, reference is made to the portion of the flow diagram illustrated in Fig. 3. In view of the derivation and initial purification of any one of the composite precipitates described above, it will be understood that the composite precipitate contains relatively large amounts of uranium and iron, a relatively small amount of chromium, and only traces of copper and nickel. The composite precipitate is first dissolved in a solvent such as HCl and the pH of the solution is adjusted to approximately 1.5 by the addition of an appropriate amount of NH4OH, whereby the solution contains the following ions: UO2++, Fe and Cr+++. The solution isthen treated with a reducing agent such as freshly prepared (NH4)2S2O4, the ammonium hyposulfite being prepared in any suitable manner, such, for example, as by the action of powdered Zll'lC on an aqueous solution of ammonia and S02. More particularly, the ammonium hyposulfite is added slowly, While the solution is stirred, care being taken never to allow the pH to exceed 5.0, whereby the solution is reduced. More particularly, the uranyl ion, UO2++, is re 'duced to the uranous ion, U++++, and the ferric ion, Fe+++, is reduced to the ferrous ion, Fe++; and no reduction of the chromic ion, Cr+++, is effected. The reduction is judged to be complete when the solution being at pH 3.0, the E. M. F. is -300 millivolts employing a platinum-saturated KCl calomel electrode couple.

To the reduced solution a carbonyl compound of the class of aldehydes and ketones, such as formaldehyde (HCHO), is added to complex the sulfite ion by forming the complex H2C(OH)SO3 ion. Thus, in aqueous solution the sulfite ion is hydrolyzed appreciably to the bisulfite ion according to the reaction:

Thereupon the formaldehyde reacts with the bisulfite ion to form the aldehydebisulfite addition compound, which is a strong electrolyte and remains in solution, sufficient formaldehyde being added so as to reduce the molar ratio of sulfite ion to uranous ion to below a value of approximately 4.0. Accordingly, the complexing of the sulfite ion may be expressed in an overall manner as follows:

This complexing of the sulfite ion prevents sulfite complex formation with the uranous ion and the consequent incomplete precipitation of uranium in the subsequent treatment. After the sulfite ion has been complexed, as explained, NHOH is added to the solution in order to bring the pH thereof to a value in the range of about 4.0 to 4.8, and preferably approximately 4.4, this treatment with ammonium hydroxide being carried out slowly, as it requires some time for the pH of the solution to settle down to a constant value, since the formaldehyde seems to engage in a side reaction with ammonia to form a certain amount of hexamethylenetetramine. When the pH of the solution is adjusted to the value mentioned, the uranium is precipitated away from the Fe++ and Cr+++ ions in the solution as U(OH)4. The solution is then filtered and the uranous hydroxide precipitate is Washed with an aqueous solution containing about one percent NH4OH and one percent NH4Cl, in order to eliminate any occluded ferrous and chromic ions.

The filtrate containing the Fe++ and Cr+++ ions is then discarded or subjected to salvage treatment in order to recover any uranium contained, while the uranous hydroxide precipitate is calcined in an inert or nonoxidizing atmosphere, such as nitrogen or hydrogen, at approximately 250 C. in order to produce U02. The uranium thus purified and in the compound form U02 is then stored for further treatment or commercial use, as previously noted.

The pH control process of purifying uranium, whereby the uranium is precipitated as uranous hydroxide, as explained above, lends itself quite well to commercial production in conjunction with the calutron method, in

7 that the uranium is sharply separated from the iron impurities and the uranous hydroxide precipitate may be readily filtered. Moreover, as illustrated, where any copper impurities that are initially present are substantially completely eliminated in the initial purification step while the copper is in its higher valence state, i. e., before the solution is reduced, an efiective separation as between uranium and copper is attained, in view of the fact that, if not so initially separated, copper in its lower valence state would be precipitated as cuprous oxide along with the uranous hydroxide. However, while desirable this is not essential, since if cuprous oxide is precipitated together with uranous hydroxide, the two may be readily separated thereafter, such as by extracting the former from the mixture by a means of a selective solvent such as NH40H, or in any other desired manner. Furthermore, the chromium impurities must be in rather Small amounts, as chromic hydroxide will be precipitated along with the uranous hydroxide in the event the chromic ion concentration of the solution is of the order of a few tenths of one percent; however, this difiiculty can be eliminated to a considerable extent by maintaining fairly high the concentration of sulfite ion in the solution, as the sulfite ion will complex the chromic ion and prevent its precipitation. In any event, it is preferred to adjust the ratio of formaldehyde, or other carbonyl sulfite-complexing agent, to hyposulfite such that the concentration of sulfite ion available in the solution for the purpose of complexing the metal cations is sufiicient to complex substantially completely the chromic ion present, without at the same time complexing the uranous ion to any appreciable extent. The amounts of the respective reagents necessary for this purpose may be calculated from an analysis of the solution undergoing treatment, or by trial runs made upon small aliquots thereof. As indicated above, it has been found generally sufficient for this purpose to conduct the procedure under conditions such that the molar ratio of sulfite ion to uranous ion is below approximately 4.0.

It will be understood that the purification of the first composite precipitate in the manner described above is productive of a first batch of U02 containing uranium of natural or normal composition with reference to U Also, the purification of the second composite precipitate in the manner described above is productive of a second batch of U02 containing uranium which is singly enriched with U Finally, the purification of the third composite precipitate in the manner described above is productive of a third batch of U02 containing uranium which is doubly enriched with U The first and second batches of U02 are then converted back to UCL; for retreatment in the first-stage and second-stage calutrons, respectively; while the third batch of U02 is available for commercial use.

More particularly, a batch of U02 is reacted with CC14. in the vapor phase at approximately 450 C. in a suitable reaction chamber, in order to produce crude U014, whereby COClz, C02, C and C12 gases are given off incident to the reaction. The crude uranium tetrachloride thus produced is then sublimed in a suitable molecular still at approximately 600 C. in order to produce a sublimate of UC14, whereby residues of U02 and U0Cl2 are produced incident to the sublimation. The residues of U02 and UOCl2 are ultimately converted to UC14. The UC14 thus produced is of very pureform and is suitable for recycling in the appropriate one of the first-stage or second-stage calutrons, in the manner previously explained. More particularly, the conversion of the first batch of U02 is productive of a first batch of UCL; containing uranium of natural or normal composition with reference to U this first batch of UCl4 is recycled in the first-stage calutron. Also, the conversion of the second batch of U02 is productive of a second batch of UCLl containing uranium singly enriched with U 3 this second batch of UCL; is recycled in the secondstage calutron.

The present process of recovering uranium from wash solutions derived from calutrons'is very effective, in view of the fact that it is quite versatile. Thus, not only may uranium be reclaimed from a wash solution con- .taining the impurities mentioned, iron and a small amount of chromium, but the wash solution may contain a variety of other impurities, such as nickel and manganese, without adversely affecting the purification. In fact, the process will handle any metal impurities of a class the divalent hydroxides of which have a solubility product greater than approximately 10*, such as iron, nickel and manganese. Moreover, the purification can be carried out as explained without particular reference to the identification of the impurities or the proportions contained in the wash solution; this feature is ,very advantageous in view of the fact that both the particular impurities, as well as the related quantities thereof, vary considerably among the different wash solutions derived from the different calutrons.

In view of the foregoing, it is apparent that there has been provided an improved process of recovering, reclaiming, purifying and converting uranium, both in metallic and compound form, in conjunction with the calutron method, whereby uranium enriched with U may be produced on a large scale in commercial quantities.

Also, it will be understood that the present process may be suitably modified so that a compound of uranium other than U014 may be treated either in the first-stage or in the second-stage calutron. For example, the calutron, as well as the conversion steps of the process, may be modified, whereby UCle, UBI, etc. may be treated in order to produce uranium enriched with U The term Uranium is employed in the present specification and claims in a generic sense, i. e., as applying to uranium whether present in elemental, ionic or compound form, unless indicated otherwise by the context.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention,

What is claimed is:

1. In a process for reclaiming uranium values from deposits formed on the parts of a calutron during the operation thereof, the steps comprising washing said parts with an aqueous solvent to form a solution containing said values and impurities, treating said solution with ammonium hyposulfite to reduce said uranium and a portion of the impurities, treating said reduced solution with formaldehyde to complex and immobilize the sulfite formed during said reduction, then treating said solution with ammonia to precipitate uranous hydroxide away from the impurities in the solution, and separating said uranous hydroxide precipitate from the solution.

2. In a process for reclaiming uranium values from deposits formed on the parts of a calutron during the operation thereof, the stepscomprising washing said parts with an aqueous solvent to form a solution containing said values in the uranyl state and Fe+++ and Cr+++ in an amount less than the order of a few tenths of one percent impurities, treating said solution with ammonium hyposulfite at a pH below 5.0 to reduce said uranium to U++++ and the Fe to Fe++ in the solution, adding ammonium hydroxide to said treated solution to adjust the pH to within the range of about 4.0 to 4.8, thereby to precipitate said uranium as'uranous hydroxide away from the Cr+++ and Fe impurities in solution, and separating 'said uranous hydroxide precipitate from the solution;

3. In a process for reclaiming uranium values from an "acidic solution containing U02- Fe+++, and Cr+++, the

steps comprising treating said solution with ammonium hyposulfite at a pH .below 5.0, to feduce the UOz and Fe+++ to U++++ and Fe++ respectively, adding formaldehyde to the reduced solution to complex and reduce the concentration of the sulfite present in said solution to below a value equivalent to 4.0 times the uranous concentration, then treating the solution with ammonia to adjust the pH thereof to a value in the range of 4.0 to 4.8 to precipitate uranous hydroxide away from the Fe++ and Cr' in the solution and separating said uranous hydroxide precipitate from the solution.

4. In a process for recovering metallic uranium values [from surfaces .upon which said values have been deposited, the steps comprising washing said surface with an acidic oxidizing aqueous solvent for said uranium to produce a solution containing UO2++, Fe+++, Cu++, Ni++ and Cr+++, treating said solution with ammonia to precipitate the uranium, iron and the major portion of the chromium away from the copper and nickel in solution, separating said precipitate from the solution, dissolving the separated precipitate to yield an acidic solution containing U02, Fe+++, and Cr+++ in an amount less than the order of a few tenths of one percent, reducing said solution with a hyposulfite at a pH of below 5.0 to yield U++++, Fe++, and Cr+++ in solution, treating said reduced solution with ammonia to adjust the pH to a value in the range of 4.0 to 4.8 to precipitate the U++++ as uranous hydroxide away from the Fe++ and Cr in said solution, and separating said uranous precipitate from the solution.

5. The process for reclaiming uranium values from the residue of uranium tetrachloride which has been deposited upon the stainless steel surface of a calutron comprising washing aid surface with water to form a solution containing said uranium together with impurities including iron and chromium in an amount less than a few tenths of one percent, treating said solution with ammonium hyposulfite while maintaining the pH below a value of 5.0 to reduce the uranyl ion contained therein to uranous and to reduce ferric ion contained therein to ferrous, treating said reduced solution with ammonia to adjust the pH into the range of 4.0 to 4.8 to precipitate uranous hydroxide away from the iron and chromium ions in said solution, and separating said uranous hydroxide from the solution.

6. In 'a process for reclaiming uranium values from an acidic solution containing UO2 Fe+++ and Cr+++, the steps comprising treating said solution with ammonium hyposulfite to reduce said UO2++ and the Fe+++ to U++++ and Fe++ respectively, treating the reduced solution with formaldehyde to complex and immobilize the sulfite formed during the said reduction, then treating the said solution with ammonia to precipitate uranous hydroxide away from Fe++ and Cr in the solution, and separating said uranous hydroxide precipitate from the solution.

7. In a process for recovering uranium values from residual halide deposits formed on stainless steel calutron parts, the steps comprising washing said parts with water to obtain an acidic aqueous solution containing UO2++, Fe+++, Cr+++, treating said solution with ammonium hyposulfite at a pH below 5.0, to reduce the UO2++ and Fe+++ to U and Fe++, respectively, adding formaldehyde to the reduced solution to complex and reduce the concentration of the sulfite present in said solution to below a value equivalent to 4.0 times the uranous concentration, then treating the solution with ammonia to adjust the pH thereof to a value in the range of 4.0 to 4.8

10 to precipitate uranous hydroxide away from the Fe and Cr in the solution, and separating said uranous hydroxide precipitate from the solution.

8. In 'a process for recovering metallic uranium values from deposits formed on a stainless steel surface, the steps comprising washing said surface with an acidic oxidizing aqueous solvent to produce a solution containing UOz++, Fe+++, Cu++, Ni and Cr+++, treating said solution with ammonia to precipitate the uranium and iron together with a portion of the chromium from the solution, dissolving the precipitate 'to form an acidic solution containing UO2++, Fe+++ and Cr+++, treating said solution with ammonium hyposulfite at a pH below 5.0 to reduce the U02++ and Fe+++ to U++++ and Pe++, respectively, adding formaldehyde to the reduced solution to complex and reduce the concentration of the sulfite present in said solution to below a value equivalent to 4.0 times the uranous concentration, then treating the solution with ammonia to adjust the pH thereof to a value in the range of 4.0 to 4.8 to precipitate uranous hydroxide away from the Fe and Cr+++ in the solution, and separating said uranous hydroxide precipitate from the solution.

9. In a process for recovering metallic uranium values from surfaces upon which said values have been deposited, the steps comprising washing said surfaces with an acidic oxidizing aqueous solvent for said uranium to produce a solution containing UO2++, Fe+++, Cu++, Ni and Cr+++, treating said solution with ammonia to precipitate the uranium, iron and chromium away from the copper and nickel in solution, separating said precipitate from the solution, dissolving the separated precipitate to yield an acidic solution containing UOz++, Fe+++, and Cr+++, reducing said solution with a hyposulfite to yield U++++ and Fe++ in solution, treating said solution with formaldehyde to complex and immobilize the sulfite formed during said reduction, treating said reduced solution with ammonia to precipitate the U as uranous hydroxide away from the Fe++ and Cr+++ in said solution, and separating said uranous precipitate from the solution.

10. In a process for recovering metallic uranium values from surfaces upon which said values have been deposited, the steps comprising washing said surfaces with an acidic oxidizing aqueous solvent for said uranium to produce a solution containing UOz++, Fe+++, Cu++, Ni++ and Cr+++, treating said solution with ammonia to precipitate the uranium, iron and chromium away from the copper and nickel in solution, separating said precipitate from the solution, dissolving the separated precipitate to yield an acidic solution containing UOz++, Fe+++, and Cr+++, reducing said solution with a hyposulfite at a pH below 5.0 to yield U++++ and Fe++ in solution, adding formaldehyde to the reduced solution to complex and reduce the sulfite concentration to a value below the equivalent of 4.0 times the uranous ion concentration, treating said reduced solution with ammonia to precipitate the U++++ as uranous hydroxide away from the Fe++ and Cr+++ in said solution, and separating said uranous precipitate from the solution.

References Cited in the file of this patent Hopkins: Chapters in the Chemistry of the Less lFamiliar Elements, chapter 18, Uranium, page 11, S-tipes Pub. Co., Champaign, Ill. (1940).

Mellor: Inorganic and Theoretical Chemistry, vol. 10, pages 173 and 175, Longmans, London (1930). (Copy in Div. 59.) 

1. IN A PROCESS FOR RECLAIMING URANIUM VALUES FROM DEPOSITS FORMED ON THE PARTS OF A CALUTRON DURING THE OPERATION THEREOF, THE STEPS COMPRISING WASHING SAID PARTS WITH AN AQUEOUS SOLVENT TO FORM A SOLUTION CONTAINING SAID VALUES AND IMPURITIES, TREATING SAID SOLUTION WITH AMMONIUM HYPOSULFITE TO REDUCE SAID URANIUM AND A PORTION OF THE IMPURITIES, TREATING SAID REDUCED SOLUTION WITH FORMALDEHYDE TO COMPLEX AND IMMOBILIZE THE SULFITE FORMED DURING SAID REDUCTION, THEN TREATING SAID SOLUTION WITH AMMONIA TO PRECIPITATE URANOUS HYDROXIDE AWAY FOR THE IMPURITIES IN THE SOLUTION, AND SEPARATING SAID URANOUS HYDROXIDE PRECIPITATE FROM THE SOLUTION. 